Panofsky, Three Essays on Style, What is Baroque? [see previous, and there may be some typos.]
update: I've added the first paragraph, which I've posted before more than once.

The late Scholastic logicians devised amusing helps to memory by which the many forms or figures of syllogism (conclusions from a major and minor premise) could be remembered. These mnemonic devices consisted of words of three syllables partly real and partly made up for the purpose. Each syllable stood for one of the three propositions, and the vowels therein signified the character of these propositions. The vowel a, for instance, denoted a general and positive statement; the vowel o, a partial and negative one. Thus the nice name Barbara, with its three as, designates a syllogism that consists of three general and positive propositions (for instance: 'All men are mortal all mortal beings need food consequently all men need food"). And for a syllogism consisting of one general and positive proposition and two partial and negative ones (for instance: "All cats have whiskers some animals have no whiskers consequently some animals are not cats"), there was coined the word Baroco, containing one a and two os. Either the word, or the peculiarly roundabout fashion of the main of thought denoted by it, or both, must have struck later generations as particularly funny and characteristic of the pedantic formalism to which they objected in medieval thought, and when humanistic writers, including Montaigne, wished to ridicule an unworldly and sterile pedant, they reproached him with having his head full of "Barbara and Baroco," etc. Thus it came about that the word Baroco (French and English Baroque) came to signify everything wildly abstruse, obscure, fanciful, and useless (much as the word intellectual in many circles today). (The other derivation of the term from Latin veruca and Spanish barueca, meaning, originally, a wart and by extension a pearl of irregular shape, is most improbable both for logical and purely linguistic reasons.)

...The twisted and and constrained mentality of the Counter Reformation period shows in innumerable phenomena: for instance, in the frightful conflicts between religious dogma and scientific thought (a problem that had not existed for a man like Leonardo da Vinci), but the most illuminating fact is perhaps the reaction of the period upon the beautiful nude in general and the classical nude in particular. Invectives were burled against Michelangelo's Last Judgement (fig. 33), which escaped destruction only by a thorough chastening. The church stated that classical marbles could be tolerated only if they were not exposed to public view; the sculptor Anunannati (at the age of seventy-one, it is true) repented in sackcloth and ashes for having made figures so scantily dressed, and the bronze fig leaf affixed to classical statues is a very characteristic invention of this period. On the other hand, both artist and art lovers were in reality no less susceptible to the beauty of classical nudes than were the Renaissance people, only their enthusiasm was marred -and sharpened- by a guilty conscience. What in the days of Raphael had been a matter of course now become a matter either of cool archeological interest or sinful excitement, and often a mixture of both.

In Bronzino’s Descent into Limbo (fig. 12) the Eve is a literal adaptation of the Venus of Knidos (fig. 34), much more archaeological than in any work of Raphael; but just this combination of classic beauty with a bashful posture and a seeming intangibility makes the figure almost ambiguous. The beholder feels that beauty is looked upon as something dangerous or even prohibited, and for this very reason is struck by these frozen crystalline nudes as by something more voluptuous and intoxicating than the straightforwardness of High Renaissance art or the sensual brio of the Baroque.

It is therefore not by accident that the Rococo or Louis XV style of the eighteenth century, striving for emotional values of a more or less lascivious kind, shows often an unmistakable similarity to the later phase of mannerism. The Amor and Psyche by Jacopo Zucchi, (fig. 35), a pupil of Vasari, in the Borghese Gallery (1589) strikes us as an actual anticipation of Charles Joseph Natoire’s representation of the same scene in the decoration of the Hôtel de Soubise (fig.36) completed 150 years later, in I739. This the proud and melancholy remoteness of mannerist portraits eloquently expresses the interior tensions or “inhibitions” of the Counter Reformation period, whether we consider a young man such as the Ludovico Copponi (fig.32) in the Frick Collection, or a great lady such as Eleanora of Toledo Grandduchess of Tuscany, as portrayed by Bronzino (fig. 37).

Bernini

A Baroque portrait, however, is free and open to the world again. The attitude of Bernini’s Costanza Buonarelli (fig. 38) [on the left here] sensuously cheerful, throbbing with unrepressed vitality, harmonious in spite of her susceptibility to every kind of impression and emotion. The Baroque (I am speaking only of Italy where the style originated) had overcome the crisis of the Counter Reformation. A modus vivendi had been found in every field; scientists were no longer burnt like Giordano Bruno (whose death might he called an emphatically manneristic occurrence, while the release of Campanella by Urban VII was a Baroque event); Roman sculptures were no longer hidden in cellars; the system of the church was now so powerful that it could afford to be tolerant towards any vital effort, and more than that:it would gradually assimilate and absorb these vital forces, and finally allow the very churches to be filled with that visual symphony of gay putti, glittering gold and theatrical sceneries as seen in the Cathedra Petri. In the field of portraits this gorgeous decoration has a parallel in that late bust by Bernini of Louis XVI (fig. 39), the triumphal outburst of the new freedom gradually conquered during the seventeenth century.

The release or deliverance achieved by the Baroque period can be observed in every field of human endeavor.The Florentine intermedios of the manneristic theater (similar to the English masks) abounded in such complicated allegories as seen in the Intermedio of 1585 and 1589 where the conclusion of Plato’s Republic appeared on the stage, including the Planets, the Harmony of the Spheres, the Three Goddesses of Fate, and even Necessity, holding the adamantine axis of the Universe (fig. 40). We happen to possess the diary of a nobleman who saw this play and stated that it was very beautiful but nobody could understand what it was all about. A few years later those allegories were replaced by the modern opera, full of natural emotions and tuneful melodies (Rinuccini’s Daphne, 1594; Monteverdi’s Orpheus, a bit later). The very style of writing had assumed a specific manneristic character all over the continent (Gongorism in Spain, Euphuism in England: Lyle, Greene and Donne). This too was overcome by Cervantes and Shakespeare. A beautiful instance is Shakespeare's Winter’s Tale (1610-11) deliberately ridiculing the euphuistic prose of the courtiers, and opposing to it the emotional and even versified, but beautifully natural, profoundly human speech of the main characters.